Carbon monoxide sinks

At present it appears that there are two major carbon monoxide sinks. The first is provided by the soil surface. Thus, laboratory experiments show that the CO absorbing capacity of different soils can be very important (see Seiler, 1974). The generalization of the results of these laboratory works gives a value of 450 x 1061 yr 1 for the global sink intensity (see Table 7). An other possibility is the reaction of carbon monoxide with OH radicals which removes CO rapidly from the air. In the previous section we have discussed the chemical destruction of CH4 by OH. One end product of these processes is carbon monoxide (see [3.2]) which also reacts with free radicals to form carbon dioxide in the following way (e.g. Bortner et al. 1974)... 

The oxides are gaseous and do not undergo reactions in the atmosphere that produce aerosol particles. Carbon monoxide is a relatively inert material with its main sinks in the atmosphere via reactions with free radicals, e.g.,... 

An important example of an atmospheric oxidation reaction is found in the main sink for carbon monoxide ... 

The SOFC can be modelled as one unit consisting of two parallel operating SOFCs fed with hydrogen and carbon monoxide. The irreversible effects including mixing are described by <+c < 1. The detailed reasons for these irreversibilities of the SOFC and other components are not necessary to understand the system s behaviour if they are considered properly in the system. The relation between work and heat within the single components and the temperatures of the heat sources and the heat sinks is the important issue here. The SOFC can be used as heat source of the fuel processing and evaporation. The required temperature levels are... 

To demonstrate the potential available, simulations were carried out for the oxidation of carbon monoxide on a palladium shell catalyst with water desorption from 3A zeolite as a heat sink, based on experimentally validated model parameters for the individual steps (Figure 16). The calculations indicated that the reaction cycle time could be lengthened by a factor of 10, to a total 20 minutes, in comparison to a simple regenerative process with a similar amount of inert material instead of adsorbent in the fixed bed and for the same threshold for temperature deviation from the initial value. 

The main sink for methane in the atmosphere is oxidation by OH radical to carbon monoxide, which in turn is oxidized to carbon dioxide according to the reaction scheme first proposed by Levy (1971) and McConnell et al. (1971) ... 

Table 9.3. Global carbon monoxide sources and sinks fluxes in units of 1012 moles C y1. (After Seiler, 1974.)...

As stated above, an event that leads to the disablement and sinking of a submarine is likely to also cause on-board fires. The toxic gases produced as combustion products could include ammonia, carbon monoxide, hydrogen... 

Carbon monoxide (CO) strongly influences the concentration of the radical OH in the tropical atmosphere. CO oxidation can lead to either production or destruction of ozone, depending on the NOx mixing ratio. Tropical soils are either a sink or a weak source of CO, where photochemical oxidation of methane and other hydrocarbons and biomass burning emissions are the predominant CO sources. 

There was a lot of discussion about the carbon monoxide in the atmosphere. You pointed out that through free radicals carbon monoxide is oxidized to carbon dioxide. Do you believe that this is the real sink for carbon monoxide, in other words, that the scheme you described is really representative for sink for carbon monoxide ... 

Johnson J. E. and Bates T. S. (1996) Sources and sinks of carbon monoxide in the mixed layer of the tropical South Pacific Ocean. Global Biogeochem. Cycles 10, 347-359. 

Carbon monoxide (CO), a toxic gas, is produced during combustion, both in wildfires and in fuel-burning devices CO also can be produced and consumed by bacterial activity. The presence of CO may indirectly increase the atmospheric mixing ratios of other gases by competing for oxidant species (such as the hydroxyl radical, OH-), thereby decreasing the oxidation rates of the other gases. This competition for oxidant species is believed to be one reason for the current increase in atmospheric methane, whose major atmospheric sink is reaction with the hydroxyl radical. 

The reaction of CCl with CO is reported to result in the formation of considerable quantities of phosgene [1824a], and it is interesting to speculate upon the carbon monoxide behaving as a thermodynamic sink for dichlorine in the well-known and industrially operated reaction [2165] ... 

Thus the net effect of dissociating nitrogen dioxide is neutral. Net production of tropospheric ozone occurs as a result of other reactions that convert NO into NO2 without destroying ozone. There are many such reactions, most of which involve the photooxidation of chemicals like carbon monoxide, methane and other hydrocarbons. Since these are produced by traffic and industrial processes, ozone production is a feature of polluted regions, and ozone itself is considered a pollutant at low levels of the atmosphere where it is detrimental to human and other life forms. Sinks of ozone include photodissociation and reactions with OH and HO2 (as in the stratosphere) and deposition. 

O.C. Zafiriou, S.A. Andrews, W. Wang. Concordant estimates of oceanic carbon monoxide source and sink processes in the Pacific yield a balanced global blue-water CO budget, Global Biogeochem. Cycles, in press. 

It is assumed that the majority of carbon monoxide is removed from the atmosphere by these reactions. Seiler (1974) hypothesizes that the yearly CO loss in the troposphere due to [3.5] and [3.7], is (1940-5000) x 1061 yr-1 The corresponding figure for the stratosphere is estimated to be 110 x 106 t yr-1 (see Table 7). In contrast, Warneck (1974) speculates that the global atmospheric strength of this sink is much smaller than the Seiler s figure. Finally, according to the calculations of Ehhalt and Schmidt (1978) about (1500-2900) x 1061C02 is produced yearly from CH4 by reaction steps [3.4], [3.2], [3.5] and [3.7]. On the basis of these data for the schematic representation of the atmospheric pathways of carbon a value of 2800 x 106 t yr 1 expressed in C02 will be accepted (see Fig. 8, p. 46) for this sink term. 

It can be seen that the great majority of carbon is cycled in the atmosphere as carbon dioxide. Thus, although the oxidation of CO provides an important sink, the process does not supply an important C02 source. It follows from the data given that the residence times of methane, carbon monoxide and carbon dioxide are 5.0 0.25 and 5.2 years, respectively. 

Oxygen gas reacts with the carbon anodes (at elevated temperatures) to form carbon monoxide, which escapes as a gas. The liquid aluminum metal (m.p. 660.2°C) sinks to the bottom of the vessel, from which it can be drained from time to time during the procednre. 

A fairly general treatment of trace gases in the troposphere is based on the concept of the tropospheric reservoir introduced in Section 1.6. The abundance of most trace gases in the troposphere is determined by a balance between the supply of material to the atmosphere (sources) and its removal via chemical and biochemical transformation processes (sinks). The concept of a tropospheric reservoir with well-delineated boundaries then defines the mass content of any specific substance in, its mass flux through, and its residence time in the reservoir. For quantitative considerations it is necessary to identify the most important production and removal processes, to determine the associated yields, and to set up a detailed account of sources versus sinks. In the present chapter, these concepts are applied to the trace gases methane, carbon monoxide, and hydrogen. Initially, it will be useful to discuss a steady-state reservoir model and the importance of tropospheric OH radicals in the oxidation of methane and many other trace gases. 

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